(CNN) – Secretary of State John Kerry insisted Sunday that the interim agreement to halt Iran’s nuclear program makes Israel safer - though Israel says the agreement has exactly the opposite effect.

“We believe very strongly that because the Iranian nuclear program is actually set backwards and is actually locked into place in critical places, that that is better for Israel than if you were just continuing to go down the road and they rush towards a nuclear weapon,” Kerry said in an interview that aired Sunday on CNN’s “State of the Union” - just hours after world powers and Iran reached the historic agreement.Follow @politicaltickerFollow @KilloughCNN

The initial six-month deal slows Iran’s nuclear development program in exchange for lifting some sanctions, while a more formal agreement is worked out.

More specifically, Iran will be required to dilute its stockpile of uranium that had been enriched to 20%. Its stockpiles should be diluted below 5%, the level needed for nuclear power plants. Iran will also have to cut back on constructing new centrifuges and enrichment facilities, and freeze essential work on its heavy-water reactor under development at Arak.

Israeli Prime Minister Benjamin Netanyahu told reporters that the agreement is far from acceptable, citing the easing of sanctions as major point of contention.

"What was concluded in Geneva last night is not a historic agreement, it's a historic mistake," Netanyahu said. "It's not made the world a safer place. Like the agreement with North Korea in 2005, this agreement has made the world a much more dangerous place."

But Kerry argued the sanctions part of the agreement is hardly a boost for Iran. The deal says that the U.S. will provide $6 billion to $7 billion in sanction relief — just a drop in the bucket compared to the roughly $100 billion in foreign exchange holdings that are inaccessible to Iran because of sanctions, the White House says.

“The basic architecture of the sanctions is staying in place. There is very little relief. We are convinced over the next few months, we will really be able to put to the test what Iran's intentions are,” Kerry told CNN chief political correspondent Candy Crowley.

In a separate interview with ABC's "This Week," Kerry acknowledged that the agreement doesn't dismantle Iran's nuclear program. But he said that strategy is "the next step" in negotiations. He also hit back against criticism that the agreement failed to completely tear down Iran's nuclear program.

"While we go through these next six months, we will be negotiating the dismantling," he said. "But you can't always start where you want to wind up."

"You cannot sit there and pretend that you're just going to get the thing you want, while they (Iran) continue to move towards the program that they've been chasing," he said.

Asked whether the agreement signals a new relationship between the U.S. and Iran, Kerry said it marks a step forward, but Iran still has a long way to go.

"We have no illusions. This is not going to change in one fell swoop overnight. We have a long building process to engage in here. We need to put to test Iran's words and intentions without any cobwebs, without any false assumptions, without any illusions. This is a hard road," he said. And, he added, "We will stand by Israel 100%."

Several Republican lawmakers in Congress have already come out against the agreement, siding with Israel. But Kerry said on ABC he feels confident "Congress will recognize that this deal actually has a great deal of benefit in it."

"And of course, (Obama) always has every other option available to him as commander in chief," Kerry said, answering a question about whether the President would veto a congressional vote for new sanctions or whether he would bypass Congress altogether.

– CNN’s Faith Karimi contributed to this report.

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